1996 GTI 717 Floating Ring very hot and DESS question

[killerk]

Hi All,
Reading these forums help tremedously so thanks to everyone out there. I have a couple simple questions that I can't find answers to. This 1996 GTI was given to me (yes, free). It is cosmetically in good shape but hadn't run since 2003. To make a long story short -- the previously stuck engine is now running after a day's work. Longevity is a questionable but things seem solid after numerous 5-10 minute runs on a garden hose.
Questions:
1. The floating ring and rubber boot around the driveshaft gets boiling hot. Literally, after running a few minutes, I shut it off and when I disconnected the garden hose I dribbled some water back there and it vaporized instantly. It is so hot that it can't be touched. Also, when revving it up a little, the boot will start to vibrate like crazy. I can feel it through the whole machine and it sounds awful, I though I was loosing a rod bearing at first. If I touch it to stabilize it (with gloves on), it calms down and the vibrations go away until I let go. How hot does this thing get and how do I stop the vibration?
2. The DESS system freaks me out. It hasn't caused an issue but it seems like something that could go haywire at some point and cost a fortune to remedy. What is the reliability of it? Is it able to be bypassed?
Thanks a bunch for reading.

 

[LouDoo]

O.K., I think your talking about the carbon seal, and yes it will get hot is you're running it on the hose, that's the reason you should only run it on the hose for a few minutes. When running in the water, the carbon seal is actually cooled by design by the water, it's actually designed to leak a little. Hopefully you haven't damaged the carbon seal, too much.

The DESS system is a security system attached to the MPEM (the computer), I have personally found both systems to be totally reliable, I have never had a problem with either. BTW, I have a 96GTI, it's a great ski, it's a cruiser.

Lou

 

[luish]

Hey!

1. You can not run the engine that long on hose. There is a carbon seal ring that gets cooled with water from under the pwc. Running that long can damage the seal and make water go in while riding.

2. Have not had problem with my dess system yet, hope not to have anytime soon. Sometimes when they fail I have read that cleaning the post will fix it, if not, changing it.

Luis...

 

[killerk]

Thanks Lou,
That makes perfect sense to me and I sort of figured as much. I hope I didn't damage it, I didn't realize what was going on. But, I never run it very long on the hose. Only long enough to do some checking and basic carb adjustments. I'll be getting in the water this weekend to furthur test things out.
If I did damage the carbon, do they vibrate? Better yet, how do I know if it is damaged? I suspect that with water behind it, it may not go crazy.
It seems like a nice machine and I like cruisers for the family. My other one is an old Yamaha Wave Venture, a cruiser as well.

Jerry

 

[LouDoo]

If you damaged the carbon seal you will have cavitation.

Lou

 

[killerk]

Hi Luis,
How long can it be run on the hose? It is only running for a few minutes at a time. I will cease and desist at once though. I hope it is OK. My only other experience with pwc's is an old Yamaha, it didn't seem to mind, at least so far. I will be more diligent in the future about being careful on both machines.
I suppose I will know if I damaged it when I get it in the water and it still vibrates or I start flooding the bilge.
Thanks,
Jerry

 

[killerk]

Hi Lou,
Please explain further if you have time. Isn't cavitation is the creation of air pockets around the impeller? How does the carbon seal prevent this?
Thank you for your time.
Jerry

 

[Coastiejoe]

As Lou stated, if you hurt the carbon seal you will get cavitation. I just want to point out it will be from air bypassing the seal from the INSIDE of the hull. Thus, cavitation

The seal is designed to "leak" water as the ski runs. This is to cool and lubricate the seal. If you damaged it, it will leak more than the norm and when you are going fast it will suck air right out of the hull..

 

[bell99man]

Get a flash light and pull back on the rubber boot and carbon ring. Look at the black part and the stainless part. Both surfaces should be smooth. I think I melted one and I never ran it very long either. I used something called salt away at the coast and I think I let it run a little long when flushing the motor. I think I will use 2 hoses on a y-connector next time.

If it is to rough look up MinneTonka4me on here. Nick can find you a good used one cheap vs. new.

 

[killerk]

Thank you everyone for your assistance. I understand its function much better now. I did pull the boot back and check both surfaces out. They are both nice and smooth so it may be OK. I will know this weekend I guess. I will be taking it easy on the poor thing since it has been sitting so long, compression is 135 in both cylinders so that much looks good. Plus, I need to ride it a while to trust it more for the long rides.

I wonder, if I make a simple compression tool to hold the boot/carbon seal off of the floating ring a little, can I run the pwc longer on the hose if needed? Does it damage the pump at all to run it on a hose too long?

Jerry

 

[LouDoo]

You can run on the hose longer, just keep the carbon seal cool, spray some water on it. However running on the hose isn't going to tell you much, you really need to run it in the water. You won't damage the pump running it on the hose.

I'm afraid I've got some bad news 135psi is not good, ideally your compression should be 150psi. 135 is not terrible but it's marginal much less and you're looking at a rebuild, you should be able to get a season, maybe a little more. I checked my 96GTI last month, 147, 145psi.

Lou

 

[killerk]

Hi Lou,
Thanks for the input, at least 135 is only 10% off target. I was surprised it had that much considering how long it sat and the condition of the upper portion of the cylinders.
If it last the rest of the summer, I'm happy. An upper end rebuild isn't too hard and depending of what is needed, not too expensive if it just needs deglazed and rings.
Wishfull thinking...
Jerry